An inverter chassis is typical formed as a base plate or frame on which components are mounted. Brackets are coupled to the base plate and the components are then bolted to the brackets. The chassis typically used to house a 2500 Watt inverter for use in a tracked vehicle such a personnel carrier tracked mobile artillery vehicle or a tank are required to withstand very high levels of shock and vibration. To control or to eliminate warping and flexing in vibration tests with limits as high as 100 Gs, conventional designs stiffen the structure by increasing the thickness of the base and frame materials and also the plating from which internal mounting brackets are formed. As the weight of the major power components such as the output transformer and associated power switching function modules increases, and as their form factor changes and grows, the size and corresponding weight of the resulting chassis is driven to a higher limit. Inverters purchased by the military for use in mobile vehicles compete within categories that have having a given input voltage and a given output voltage and power range largely on the basis of size, weight and cost with reliability being held as a very high priority consideration.
In the past, conventional units have used a large silicon steel E-Core design for the output transformer. An E-core transformer is typically formed and mounted using holes at the four corners of the core laminations. Bolts are passed through the corner holes from a mounting bracket to secure the transformer. Clearance must be provided for wire on the center leg bobbin or on each of two end leg bobbins. The bobbins themselves must be secured by bonding to a core leg or legs. The form factor of an E-Core transformer is less efficient volumetrically than the form factor of a toroidal transformer because the bobbin or bobbins are eliminated. Some toroidal cores use a non magnetic core covering or can to contain the tape material. Larger cores are bonded and then wrapped. One disadvantage of a steel tape wound toroid core is that there are no convenient bolt for mounting as discussed in connection with the holes at the corners an E-core. The absence of a convenient, mounting arrangement may partially be the reason for the absence of use of toroidal transformers in high wattage output 60 Hertz inverters. Winding a steel tape wound toroid core is more complex than winding a bobbin for an E-core. Toroid cores require a special machine and the use of a shuttle which is preloaded with the wire to be placed on the core. However, once the wire lengths are determined, the assembly can be largely automated.